Preparation and microwave dielectric properties of C_(sf)/Si_3N_4 composites

The Csf/Si3N4 composites were prepared by hot-press sintering method using α-Si3N4 power,short carbon fibers and La2O3-Y2O3 sintering additives. The mechanical and microwave dielectric properties of Csf/Si3N4 composites were studied and discussed. The results show that the addition of the short carbon fibers can not destroy the relative density of the sintered samples,but it deteriorates the flexural strength of the sintered samples,so the flexural strength of the silicon nitride matrix is the highest among the samples. The real part(ε′) and the imaginary part(ε″) of the permittivity of Csf/Si3N4 composites greatly increase with increasing volume fraction of the short carbon fibers,achieve the maximum 73.1 and 101.5,respectively. A strong frequency dependence of the imaginary part(ε″) of the permittivity is observed.

The CJSi3N4 composites were prepared by hot-press sintering method using α-Si3N4 power, short carbon fibers and La2O3-Y2O3 sintering additives. The mechanical and microwave dielectric properties of CjSi3N4 composites were studied and discussed. The results show that the addition of the short carbon fibers can not destroy the relative density of the sintered samples, but it deteriorates the flexural strength of the sintered samples, so the flexural strength of the silicon nitride matrix is the highest among the samples. The real part （ε3 and the imaginary part （ε＇3 of the permittivity of CsfCSi3N4 composites greatly increase with increasing voltmae fraction of the short carbon fibers, achieve the maximum 73.1 and 101.5, respectively. A strong frequency dependence of the imaginary part （ε″） of the permittivity is observed.